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排序方式: 共有762条查询结果,搜索用时 343 毫秒
101.
针对产紫青霉(Penicillium purpurogenum)Li-3发酵生产β-葡萄糖醛酸苷酶存在的碳代谢阻遏现象,研究β-葡萄糖醛酸苷酶的高效诱导表达策略。在发酵条件优化的基础上,建立了新的产酶诱导工艺:葡萄糖的初始质量浓度5 g/L,在葡萄糖耗尽时加入20%诱导剂(10 g/L GL+1.2%Tween80)进行诱导,每24 h添加1次诱导剂,诱导72 h后立即转到40℃摇床发酵48 h。采用该工艺进行发酵,菌体出现了"二次生长"现象,比酶活从647.99 U/mL提高至2 356 U/mL,提高了近3倍。 相似文献
102.
103.
Greenhill AR Blaney BJ Shipton WA Frisvad JC Pue A Warner JM 《Letters in applied microbiology》2008,47(4):342-347
AIMS: To assay sago starch from Papua New Guinea (PNG) for important mycotoxins and to test fungal isolates from sago for mycotoxin production in culture. METHODS AND RESULTS: Sago starch collected from Western and East Sepik Provinces was assayed for aflatoxins, ochratoxin A, cyclopiazonic acid, sterigmatocystin, citrinin and zearalenone and all 51 samples were negative. Frequently isolated species of Penicillium (13), Aspergillus (five) and Fusarium (one) were cultured on wheat grain, and tested for the production of ochratoxin A, cyclopiazonic acid, sterigmatocystin, citrinin, patulin and penicillic acid. All 12 isolates of P. citrinin and one of two A. flavipes isolates produced citrinin. A single isolate of A. versicolor produced sterigmatocystin. No other mycotoxins were detected in these cultures. CONCLUSIONS: No evidence was found of systemic mycotoxin contamination of sago starch. However, the isolation of several mycotoxigenic fungi shows the potential for citrinin and other mycotoxins to be produced in sago stored under special conditions. SIGNIFICANCE AND IMPACT OF THE STUDY: Sago starch is the staple carbohydrate in lowland PNG and the absence of mycotoxins in freshly prepared sago starch is a positive finding. However, the frequent isolation of citrinin-producing fungi indicates a potential health risk for sago consumers, and food safety is dependant on promoting good storage practices. 相似文献
104.
Penicillium citrinum β-keto ester reductase (KER) can catalyze the reduction of methyl 4-bromo-3-oxobutyrate (BAM) to methyl (S)-4-bromo-3-hydroxybutyrate with high optical purity. To improve the thermostability of KER, protein engineering was performed
using error-prone polymerase chain reaction-based random mutagenesis. Variants with the highest levels of thermostability
contained the single amino acid substitutions L54Q, K245R, and N271D. The engineered L54Q variant of KER retained 62% of its
initial activity after heat treatment at 30°C for 6 h, whereas wild-type KER showed only 15% activity. The L54Q substitution
also conferred improved enantioselectivity by KER. An Escherichia coli cell biocatalyst that overproduced the L54Q mutant of KER and glucose dehydrogenase as a cofactor regeneration enzyme showed
the highest level of BAM reduction in a water/butyl acetate two-phase system. 相似文献
105.
106.
Mahdi Yahyazadeh Reza Omidbaigi Rasoul Zare Hossein Taheri 《World journal of microbiology & biotechnology》2008,24(8):1445-1450
The antifungal action of four essential oils of Foeniculum vulgare (fennel), Thymus vulgaris (thyme), Eugenia caryophyllata (Clove) and Salvia officinalis (sage) was tested in vitro against Penicillium digitatum Sacc. Direct contact and vapour phase were used to test the antifungal activity of these essential oils against P. digitatum that is responsible for green mould rot of citrus fruits. The vapour phase and direct contact of clove and thyme essential
oils exhibited the strongest toxicity and totally inhibited the mycelial growth of the test fungus. Thyme and clove essential
oils completely inhibited P. digitatum growth either when added into the medium 600 μl l−1 or by their volatiles with 24 μl per 8 cm diameter Petri dish. In in vitro mycelial growth assay showed fungistatic and fungicidal
activity by clove and thyme essential oils. Sage and fennel oils did not show any inhibitory activity on this fungus. Scanning
electron microscopy (SEM) was done to study the mode of action of clove oil in P. digitatum and it was observed that treatment with the oil leads to large alterations in hyphal morphology. 相似文献
107.
Hein Trip 《生物化学与生物物理学报:生物膜》2004,1667(2):167-173
The gene encoding an aromatic and neutral aliphatic amino acid permease of Penicillium chrysogenum was cloned, functionally expressed and characterized in Saccharomyces cerevisiae M4276. The permease, designated PcMtr, is structurally and functionally homologous to Mtr of Neurospora crassa, and unrelated to the Amino Acid Permease (AAP) family which includes most amino acid permeases in fungi. Database searches of completed fungal genome sequences reveal that Mtr type permeases are not widely distributed among fungi, suggesting a specialized function. 相似文献
108.
从用于堆肥的水稻秸秆中初筛出一株高效纤维素降解菌L-06, 根据18S rRNA基因序列和菌株形态分析, 初步鉴定该菌为斜卧青霉(Penicillium decumbens)。研究了液体发酵培养基中氮源、碳源、表面活性剂、培养温度、起始pH以及接种量对该菌株各纤维素酶活力的影响。在最适条件下, 该菌的b-葡萄糖苷酶(BGL)、外切纤维素酶(CBH)于培养第3天酶活力分别达到1662 u/mL和2770 u/mL; 内切纤维素酶(EG)、滤纸糖化力(FPase)于培养第4天酶活力分别达到18064 u/mL和4035 u/mL。在产酶优化实验中, 该菌的EG和CBH在pH10的培养条件下分别保持了70%和43%的酶活性; 在50oC培养条件下EG和CBH分别保持了68%和59%的酶活性。表现出了耐热, 耐碱的特性。 相似文献
109.
青霉菌立体选择性环氧化顺丙烯磷酸产生磷霉素 总被引:10,自引:0,他引:10
由土壤中分离出一株青霉 (Penicilliumsp .) ,编号F5,能选择性的将顺丙烯磷酸环氧化为磷霉素 ,在pH7 5、2 8℃、2 80r min条件下培养 6d ,底物浓度 0 3%时 ,产物浓度达 2 2mg mL ,产率 41 % ;底物浓度 0 6%时产率 8%。转化产物经磷霉素敏感菌生物检测 ,TLC检测 ,并与标准品比较 ,确证为磷霉素。 相似文献
110.
培养基对海洋青霉菌抗真菌活性物质的影响 总被引:2,自引:0,他引:2
研究了培养基的配方、培养条件和培养时间对海洋青霉M-182菌株产生抗真菌活性物质(M-182A)的影响,以期获得高效价的M-182A。结果表明:用海水配制经改良的高氏1号培养基(高氏1号+0.1%蛋白胨+2%海带汁),28℃培养96-108h,M-182A的相对效价最高。 相似文献